Absorptivity extinction coefficient

The microenvironment in water-containing AOT-reversed micelles has a marked effect on the spectral properties of flnorescein. The absorption peaks are red-shifted by about 10 nm from the corresponding positions in aqueous solution, the absorption extinction coefficient increases with R, and the fluorescence is more effectively quenched in AOT-reversed micelles than in aqueous solution [149],... 

Perhaps the most widely studied chemical class of near-IR absorbers are the cyanines. The chemistry and synthetic routes to cyanines are discussed in other parts of this book (Chapter 2, section 2.3.1.4 and Chapter 3, section 3.5.1.7). The factors influencing the position of their absorption maxima and molar absorption (extinction) coefficients areC ... 

Phenolic substances all absorb UV light, and all of them have some absorbance at 280 nm. This property can be used to determine phenolics by spectral analysis. One problem with this method is that each class of phenolic substances has a different absorptivity (extinction coefficient, e) at 280 nm. Thus, the results cannot be related to any specific standard and are reported directly in absorbance units (AU). This also means that disparate wines (or other disparate samples) are difficult to compare with this method, as they are likely to have very different compositions. 

Quantitative determination of conformational disorder, in addition to assignments of the spectral features, requires accurate calibrations of relative absorptivities (extinction coefficients) for the various bands. These were calculated with the aid of the rotational isomeric state model of Flory (22), a statistical mechanical determination of conformational disorder in alkanes. The model requires an estimate for the energies of gauche bonds, chosen from the best available experiments to be 508 +/- 50 cal/mole, and an energy for the bond pairs E, chosen to be 3000 cal/mole. The... 

The mature kernel phenotype for the triple mutant ae du su is similar to that for su (Table 3.3). Sugar concentrations of mature272 and immature270 ae du su kernels are higher than those of either of the single mutants or the double mutants ae du or ae su, while starch concentration is similar to that in su and the two double mutants. The amylose percentage is close to that of normal when measured by either the blue value test (Table 3.6) or SEC (Table 3.7). However, in contrast to normal, a major proportion of the branched polysaccharide is smaller than typical amylopectin (as is that of ae su), and it elutes from an SEC column at an intermediate position (Table 3.7). The absorbance maximum and absorptivity (extinction coefficient) of the branched polysaccharide-iodine complexes are similar to those for ae and ae su, and are characteristic of loosely-branched polymers. The absorbance maximum of the amylose-iodine complex is similar to that of normal, du, or su, but the absorptivity is lower than for either (Table 3.7). No short chain amylose has been found in ae du su starch.90... 

Integration of absorption extinction coefficient (Eq. [127]) and emission rate (Eq. [128]) gives two alternative estimates for the adiabatic gas-phase transition dipole mu (in D) within the TSM frequency-dependent mu(v) (Eq. [132])... 

There are many cases when radical absorption in the UV region overlaps with a tail of absorption of a photoinitiator or other species produced by photolysis. Optical detection may become less sensitive or impossible. Also, a transient radical may have low absorption (extinction coefficient) in the UV-vis region. For example, a... 

In this analysis of first-order kinetics, any value can be plotted against time of reaction, unless the value is proportional to the molar amount of a substrate or product for example, absorbance of a compound at a given wavelength can be used even if the molar absorption (extinction) coefficient is unknown and thereby absolute concentration can not be determined. Moreover, taking the logarithm means a reciprocal value can also be used, e.g., [Ao]/[A], where [Aq] is initial concentration of a substrate A (See Fig. 6). 

For a cloud of randomly oriented small spheroids, the spectral absorption ( extinction) coefficient is given as (Lee and Tien [189]) ... 

Irradiation in an Atlas xenon arc Weather-Ometer. Hydroperoxide concentration after irradiation, estimated from the 3400cm i.r. absorption (extinction coefficient = 70M cm" ). After 8h immersion in 3.3 x 10 m solution of I in iso-octane. 

Wavelength of maximum absorption Extinction coefficient at 7200A. Width at half-height Oscillator strength Diffusion Constant Equivalent Conductance Effective Collision Radius Ion Atmosphere Relaxation Time at /x = 0.24M Partial Molal Volume Standard Free Energy of Solvation G (e m), y-Radiation Yield Lifetime with respect to H30+ at pH 7 Lifetime with respect to H20... 

Protein pKa Maximum absorption (extinction coefficient mol i 1 cm-i) Decay t second-order (mol 11 s ) it first-order (s-l) (pH 8) End products Ref. 

The molar absorptivity (extinction coefficient) as a function of wavelength is characteristic for a molecule and is based on the functional groups within the molecule. If the molar absorptivity is known for a given molecule, its concentration in solution can be calculated using the Beer-Lambert law. 

Absorbance, Transmittance, Molar Absorption (Extinction) Coefficient, Beer-Lambert Law and Deviations from Beer-Lambert Law... 

The molar absorption (extinction) coefficient, Einstein coefficient and absorption cross-section are commonly used measures of transition probability. The first three are used for atomic and molecular species in the gas or solution phase, while the latter is commonly used in solid-state studies. These are absolute measures of absorption probability and are ultimately derived from the transition dipole moment, and are therefore all related. They can be measured experimentally firom the absorption spectrum and can, in some cases, be calculated using molecular orbital theory programs. (Note that generally MO calculations will give the oscillator strength for any forbidden transition as zero). 

The UV absorption extinction coefficient s for a protein or a nucleic acid often does not represent the true value because of the partial scattering of light. This can be corrected by the equation... 

This is actually a form of Beer s law with each B term containing both path length and molar absorptivity (extinction coefficient) terms. Most simply, the concentration is related to the optical data as... 

The existence and quantity of the end groups in the polymers is normally measured by infrared spectroscopy on a compression-molded film with a thickness of 250 pm. Most of the end groups of interest absorb in the band range of 1700-1900 cm. Table 5.22 shows the relationship between wave numbers and the end groups. The quantitative measurement of the end groups is achieved by the measurement of the absorption extinction) coefficient of each of the end... 

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